Tuesday, March 4, 2014

DNA Monday: The beauty part more relatives getting tested

Now I get it: it's way better when more relatives get DNA tested.

At first it instinctively made sense, but now that Mom's 4th cousin has been tested and her uncle and aunt also tested, along with my brother and Mom, well, it's a DNA party over here. Her husband is managing her project and I manage Mom and brother's accounts so he and I have been working together. Let's just call him "Rich" because he's rich in genealogy stuff. This guy knows how to research like a blood hound!

Rich's wife is the direct descendant of the sister of Mom's 2nd great grandmother... or the direct descendant of my 3rd great grandparents. (I had to use the Steve Morse One-Step Relationship Calculator to be sure. http://stevemorse.org/relation/calculator.html ) OK, now I'm real willing to admit that the cousins and their removal is like jello in my mind! I think I have it nailed down and then, poof, it's gone. My Family Tree Maker says one thing and Steve Morse's One-Step calculator says something else so it's operator error for sure. (I have a self-inflicted headache now.) The point being that Rich's wife and Mom and I are blood relatives. Whew.

Rich's people tested with Ancestry DNA and Mom and all of us tested with 23andMe. We met in the middle and uploaded raw files to GEDmatch. It's so lovely that there's a place to upload your raw files and compare across DNA platforms.

Rich and I are new to this, although in full disclosure I have been working with my DNA results almost a year now, stumbling as I go and learning by trial and error. But DNA for genealogy got so complex so fast that I always feel as though I've just scratched the surface! He and I spent an hour or so chatting by phone and while our conversation happily rambled here and there, we did talk about the connections that our DNA results show.

Recently I've read about "sticky" chromosome segments, ones that are passed down through multiple generations. I think I read it on Roberta Estes blog, DNAeXplained – Genetic Genealogy. Here's the recent article in which she mentions "sticky" segments. This blog post is really good at explaining a phenomenon I've seen in the results for the known relatives who have tested. By identifying known relatives and our shared segments, especially when three or more are tested, I can go look for others in the GEDmatch database who match on those chromosomes looking for the segment match.

In the case of Rich and his wife's relatives, we are looking at sticky segments for Mom and Uncle. Here's what we see on GEDmatch.

Minimum threshold size to be included in total = 500 SNPs
Mismatch-bunching Limit = 250 SNPs
Noise Reduction Threshold = 0.85
Minimum segment cM to be included in total = 5.0 cM

Chr Start LocationEnd LocationCentimorgans (cM)SNPs

Largest segment = 28.5 cM
Total of segments > 5 cM = 112.2 cM
Estimated number of generations to MRCA = 3.5

And we can go looking for matches on that loaded chromosome 13. And here's what that looked like.

Comparing Kit M120110 (Mom)   
Kit NumName
Chr Start LocationEnd LocationCentimorgans (cM)SNPs

As you can see Uncle and Mom show up as we would expect. And two other people also show up but they don't match on the same locations on chromosome 13. Too bad but we'll keep looking.

I find it astounding that those segments on CH 13 have been handed down through two descendant's lines intact! Talk about sticky!

The URL for this post is: http://nutsfromthefamilytree.blogspot.com/2014/03/dna-monday-beauty-part-more-relatives.html

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